| 摘要 |
<p>A shock absorber for use in lowering heavy structures to the sea floor comprises a cylinder (1) with a piston (2) having a heavy piston rod (3). A plurality of channels (6) extend from the bottom side of the piston (2) to its top side, where the channels are closable by means of a disk-like valve body (7) which permits fluid movement up through the piston to a cylinder chamber (20) above the piston, but not in the opposite direction. The cylinder chamber (20) is provided with a plurality of exit nozzles (21) having diminishing diameter in the direction towards the bottom (13) of the chamber (20). At the lower end of the cylinder it is provided with a number of inlet openings (19), so that when the shock absorber is lowered in the sea together with the structure, the cylinder chamber (20) will automatically fill with sea water. Due to their weight the piston (2) with the piston rod (3) will be in the lower position. When the piston rod (3) impacts against its substructure on the sea floor, it will force the piston (2) upwards in the chamber (20). The valve body (7) will close the channels (6) so that the water in the chamber (20) has to escape mainly through the nozzles (21), thus giving the shock absorber the desired resisting force. When the piston is forced into the cylinder chamber, the nozzles (21) will successively be put out of action, such that the remaining active nozzles will have a steadily reduced flow area. However, the depression velocity of the piston will concurrently become lower, so that the resistance against the piston will be substantially constant. During a further heave movement, the weight of the piston and piston rod and the large flow area in the channels (6) will cause the piston to sink faster than the heave velocity of the structure, so that the piston rod (3) remains in contact with the subsurface.</p> |
